Abstract : The goal of this paper is to develop a new method of decentralized control tuning. This method is based on Nyquist-Arrays and independently designs monovariable controllers for each loop of the plant while ensuring the robust stability of the multivariable system. It works on the optimization of a frequency criterion using the controller’s design parameters. PID controllers have been chosen in this study because of their good performances for most applications. Finally, the proposed method allows to achieve good performances and the stability is ensured thanks to the analysis of Gershgorin and Ostrowski bands.